The Bulletin. 53 



trol was lost of those factors of fertility or conditions necessary for the growth 

 of roots, with the result that the crop yield ran down to one-third. 



Chart 3 : This chart represents results obtained in Minnesota on a piece of 

 land in which there was a certain quantity of humus and a certain quantity of 

 nitrogen. The yield of corn was 50 bushels to the acre, A part of that land 

 was run to corn straight, for four years, with the result that by 1896, the 

 fourth year of corn, the humus in the soil had decreased. There was a loss of 

 3 tons of vegetable matter or humus to the acre, with a corresponding loss of 

 600 pounds of nitrogen, and a reduction in yield from 50 to 44 bushels per acre. 

 Adjoining this, a part of the land was put into a rotation consisting of oats, 

 clover, barley, and corn. The clover hay, other roughage, and some grain 

 were fed to stock, and the manure, 4i^ tons per acre, was put into the soil of 

 the corn plat. The result was that there was a gain of three-fourths of a ton 

 per acre in humus, and a corresponding gain of 40 pounds of nitrogen, and an 

 increase of crop yield to 67 bushels. 



Chart 4 : This represents some very interesting and valuable work done by 

 Dr. Hopkins in Illinois. Corn was planted on a piece of corn-belt prairie land 

 which had been in pasture for a number of years. At the beginning the yield 

 was 70 bushels per acre. That was a pretty good piece of land. On a part of 

 that farm corn was grown for thirteen years in succession, with no other crop, 

 and the result was that control over fertility was lost to the extent that the 

 yield was reduced to practically one-half the original yield, or 35 bushels. 



On an adjoining section corn and miscellaneous crops had been grown for six 

 years, also reducing the yield. Then a rotation was introduced — corn, oats, and 

 clover. At the end of seven years of this rotation the average yield of three 

 crops of corn was 69 bushels to the acre, nearly the original yield. This was 

 run as a grain farm, grain being taken from the crops and the residue turned 

 into the soil ; and thus the fertility of the land and the crop yield was very 

 nearly maintained. On an adjoining part of the farm, when the same rotation 

 was run under a system of live-stock farming, the manure produced by feeding 

 the crops was returned to the land and the yield of corn averaged si bushels 

 per acre. 



On another part of the farm the same i-otation was carried on, with an 

 addition of lime equivalent to one-half ton per acre every five years, plus an 

 annual application of 200 pounds of steamed bone-meal and 100 pounds of 

 potassium sulphate, the fertilizer costing altogether $6 per acre. The average 

 yield of corn for the last three years with the grain-growing system was 94 

 bushels and with the stock-farming system 96 bushels. 



On an adjoining part, where corn was grown continuously for six years and 

 the yield reduced, an attempt was made to increase it by the use of commercial 

 fertilizer alone. After seven years had passed, the average yield for the last 

 three years was found to be 66 bushels, but the annual cost for fertilizer was 

 $42.56 per acre. 



This chart shows that the constant cultivation of one crop tends to weaken 

 the control over fertility, and consequently to reduce the crop-yielding power 

 of the soil. It shows that better results are obtained from growing nitrogen- 

 gathering clover in rotation with other crops, that an attempt to control fertility 

 by means of commercial fertilizer without the addition of humus to the soil is 

 too expensive and unsatisfactory, and that a combination of a crop rotation 

 embracing a nitrogen-gathering legume, supplemented by a judicious quantity 

 • of commercial fertilizer, was the best means of controlling fertility and increas- 

 ing crop yields. The commercial fertilizer was made more powerful and 

 efficient when used in soil well supplied with new nitrogen-bearing humus. 



Chart 5 represents results on a farm of loose, white sand in Florida. Dur- 

 ing the first year the owner got 5 bushels of corn to the acre. He introduced 

 a rotation — corn, with cowpeas planted at the last working, followed by rye 

 in the winter, followed by velvet beans. The rye and velvet beans were grazed 

 off in the winter by cattle. The land received no manure, except that dropped 

 by the cattle when grazing on it. and no commercial fertilizer. The result 

 was that the yield had come up to 15 or 20 bushels per acre at the time I saw 

 it. These were not ver.v large yields as yet, but they show the truth of the 

 principle that filling the soil with decaying vegetable matter enables the 

 farmer to get control of fertility and increase his crop yields. 



